The present invention relates generally to a device for detecting the exhaust gas temperature of an internal combustion engine, and more particularly to an oxygen sensor located within the exhaust system which has an exhaust gas temperature sensing element deposited on the outside surface of the oxygen sensor.
In order to reduce the environmental damage that occurs due to the amount of emissions produced by automobiles, there have been strong legislative movements to require automobile producers to effectively monitor the performance of their engines. Although the monitoring and reduction of automotive emissions is a primary concern, so is the performance of the engine. With the intention of achieving optimal engine performance, a variety of approaches have been taken by automobile manufacturers in the attempt to maximize the efficiency of an engine, while producing as few emissions as possible.
One type of exhaust monitoring system incorporates an oxygen sensor. The oxygen sensor is located within the exhaust system of an automobile and is designed to detect an air/fuel ratio which is critical in the performance of a combustion engine. A specific mixture of air and fuel, otherwise known as the xe2x80x9cperfect ratioxe2x80x9d, is required to have the most favorable performance from an engine, while reducing the amount of pollutants produced.
If there is less air than the perfect ratio, fuel will be left over after combustion, resulting in what is known as a rich mixture. A rich mixture results in increased pollution due to the unburned fuel that is left following combustion. In contrast to the rich mixture, a lean mixture is obtained when there is an excess of oxygen in the air/fuel mixture. A lean mixture tends to produce more nitrogen oxide pollutants, resulting in poor engine performance and may ultimately cause damage to the engine.
In addition to monitoring the amount of oxygen present in the exhaust system, the temperature of the exhaust system must also be monitored in order to optimize engine performance. The overheating of the catalytic converter results in an increase in temperature of the exhaust gas system. This temperature increase in the exhaust gas system increases the amount of pollutants which are emitted into the environment.
With the purpose of monitoring the temperature of the exhaust system, different approaches have been taken to incorporate a temperature sensing element within the exhaust system. For example, temperature sensors have been placed as a discrete component within the exhaust system. However, this approach has certain drawbacks due to increased costs and the potential of breaking.
In order to overcome this drawback, another prior art approach incorporates a temperature sensing element within the oxygen sensor. In this approach, a temperature sensing element is printed on the heater element of the oxygen sensor. Although this approach is more popular than a separate temperature sensor, there are problems associated with it as well. For example, the existing heater element within the oxygen sensor is insulated from fluctuations in the exhaust gas temperature by the oxygen sensor""s O2 sensing element. Therefore, inaccurate readings are obtained from the temperature sensing element due to its location on the heater element. A time delay results from the exhaust gas passing over the oxygen sensor onto the heating element, wherein the prior art exhaust gas temperature sensing element is located. Therefore any response by the electronic control unit is outdated, due to the delay in time.
The present invention incorporates the use of a temperature sensing element with an oxygen sensor, but alters the placement of the temperature sensing element on the oxygen sensor. The change in location of the temperature sensing element allows for real-time feedback which can be useful in determining temperature conditions in the exhaust environment. This may include detecting misfires, changes in catalyst temperatures, as well as conditions during wide-open-throttle closed loop control.
More specifically, one object of the present invention is to incorporate a temperature sensing element on the outside of the oxygen sensor""s sense element, which results in maximizing the reading capability of the temperature sensing element. The present invention thereby overcomes the problems associated with the prior art, and optimizes the amount of real-time feedback obtained from the temperature sensing element.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.